1. Field of the Invention
The present invention relates to a disc cartridge in which a disc-shaped medium used as a recording/reproducing medium for an information processing device or the like is rotatably housed with preventing invasion of dust, etc. into the disc cartridge.
2. Description of the Related Art
Disc-type media such as an optical disc, a magneto-optical disc, etc. have been used as recording/reproducing media for portable computers, for example. When information is recorded into or reproduced from such a disc medium, a laser beam is irradiated onto a recording face of the disc medium while the disc medium is loaded and rotated in a drive device. The recording of the information on the disc medium is performed by formation of pits due to decomposition of a dye layer of the recording face, phase variation, magnetization or the like, and the reproduction of the recorded information from the disc medium is performed on the basis of variation in reflectivity or polarization angle of the laser beam.
In order to enhance the recording capacity for such disc media, it has been proposed to shorten the wavelength of a laser beam to be irradiated onto the recording face. When information recording or reproduction is carried out by using a short-wavelength laser beam, for example, a blue-violet laser beam, the laser beam is attenuated by a cover layer for protecting the recording face of the disc medium. In order to suppress the attenuation of the laser beam due to the cover layer, the thickness of the cover layer is required to be small. When the thickness of the cover layer is reduced as described above, the diameter of the spot of the laser beam on the surface of the cover layer (the exposed surface to the outside) is reduced, so that the influence of dust or the like adhering to the surface of the cover layer is no longer negligible.
Therefore, there has been used a disc cartridge having a case in which a disc medium is housed to prevent adhesion of dust, etc. to the disc medium. Such a cartridge is designed to have an aperture through which the center hole portion formed at the center portion of the disc medium and a part of the recording face (cover layer) of the disc medium are exposed to the outside, and a shutter member for opening/closing the aperture.
With this construction, the aperture of the disc cartridge is normally closed by the shutter member to prevent invasion of dust, etc. into the disc cartridge, that is, adhesion of dust or the like to the disc medium. The aperture is opened by the shutter member through the loading of the disc cartridge into the disc drive device, whereby holding of the center hole portion by a rotating spindle shaft and approach of the laser head to the recording face (irradiation of the laser beam) are allowed.
Such a disc cartridge is disclosed in Japanese Laid-open Patent Application No. 2000-30394. The disc cartridge disclosed in this publication will be described hereunder with reference to FIG. 43.
FIG. 43 is an exploded perspective view showing a disc cartridge 400.
As shown in FIG. 43, the disc cartridge 400 comprises an upper shell 402 and a lower shell 404 which are joined to each other to form a case, and a disc-shaped disc medium 406 is rotatably housed in the case. The lower shell 404 is equipped with a cylindrical wall 404 A in which the disc medium 406 is housed, and an aperture 408 which is cut out to extend from the front portion of the cylindrical wall 404 A to the substantially center portion of the lower shell 404.
The aperture 408 comprises a laser-head inserting (approaching) aperture 408A extending in the radial direction of the disc medium 406, and a rotating spindle-shaft inserting aperture 408B corresponding to the center hole portion 406A of the disc medium 406, the laser-head inserting aperture 408A and the rotating spindle-shaft inserting aperture 408B being formed continuously with each other, and the aperture 408 is used to access the disc medium 406.
The disc cartridge 400 is further equipped with a first shutter member 410 and a second shutter member 412 for opening/closing the aperture 408. The first shutter member 410 has a shutter main body 414 for mainly opening/closing a substantially trapezoidal aperture 408A, and a shutter guide portion 416 which is erectly provided at the front end of the shutter main body 414, formed in the arcuate shape corresponding to the cylindrical wall 404A, guided by the cylindrical wall 404A and opens/closes the notch portion (the start portion of the aperture 408) of the front portion of the cylindrical wall 404A.
One end portion of the shutter guide portion 416 is joined to a thin-plate type operating member 418 which can be deformed in the thickness direction, and a block-shaped operating portion 418A is provided to the tip of the operating member 418. The shutter guide portion 416 and the operating member 418 are formed integrally with each other, or they are formed separately from each other and then secured (fixed) to each other by adhesion, welding, press-fixing or the like to be joined to each other. Accordingly, the tension (operating force) which usually acts on the operating member 418 is transferred to the shutter guide portion 416 to rotate the shutter guide portion 416.
The second shutter member 412 is rotated around the rotational shaft 412C provided at the end portion thereof to mainly open/close the aperture 408B. A torsion spring (not shown) is equipped to the rotational shaft 412C, and the second shutter member is urged by the torsion spring so as to close the aperture 408B.
The disc cartridge 400 is equipped with a cover member 420 disposed so that the first and second shutter members 410, 412 are movable between the cover member 420 and the lower shell 404. The cover member 420 is provided with an aperture 422 to access the disc medium 406, which corresponds to the aperture 408.
In the disc cartridge 400, when the disc medium 406 is unused, the shutter main body 414 of the first shutter member 410 and the second shutter member 412 are disposed to close the apertures 408, 422 while the end faces 414A, 412A thereof abut against each other. Specifically, the first shutter member 410 mainly closes the aperture 408A, and the second shutter member 412 mainly closes the aperture 408B. Under this state, the shutter guide portion 416 of the first shutter member 410 closes the start portion of the aperture 408A (the cut-out portion of the cylindrical wall 404A).
On the other hand, when the disc medium 406 is used, the disc cartridge 400 is loaded in the drive device, and the end faces 414A, 412A of the first and second shutter members 410, 412 are moved in such a direction that they are separated from each other, thereby opening the apertures 408, 422.
Specifically, when the operating portion 418A fixed to the tip of the operating member 418 of the first shutter member 410 is moved in the direction of an arrow P along a guide groove 424 on the side surface of the case in connection with the loading of the cartridge into the drive device (the operating member 418 is drawn), the first shutter member 410 is rotated in the direction of an arrow Q around the axial center of the cylindrical wall 404A (that is, the disc medium 406) while the shutter guide portion 416 is guided along the outer peripheral surface of the cylindrical wall 404A.
Following this rotation, the first shutter member 410 presses a press-subjected piece 412B located along the end face 412A of the second shutter member 412 through a press piece 414B located along the end face 414A of the first shutter member 410 to rotate the second shutter member 412 in the direction of an arrow R around the rotational shaft 412C. That is, the first shutter member 410 and the second shutter member 412 are rotated in the different directions while interlocked with each other, thereby opening the apertures 408, 422. Under this state, a window portion 416A formed in the shutter guide portion 416 is located at the front portion of the cylindrical wall 404A to open the cut-out portion (aperture 408A) of the cylindrical wall 404A.
On the other hand, when the apertures 408, 422 thus opened are closed again, the operating portion 418A is pressed in the opposite direction to the direction of the arrow P by the drive device, or the first shutter member 410 is pressed through the press piece 414B by the press-subjected piece 412B of the second shutter member 412 with the urging force of the torsion spring, whereby the first and second shutter members 410, 412 are rotated in the closing direction of the aperture 408, etc. (in the opposite directions to the directions of the arrows Q, R) while interlocked with each other, thereby closing the apertures 408, 422.
As omitted from the drawings, a modification of the interlocking means for interlocking the first and second shutter members 410, 412 is described in the above publication. The interlocking means according to this modification is equipped with a projecting portion disposed away from the rotational center of the first shutter member 410 (the axial center of the cylindrical wall 404A) and an elongated hole in which the projecting portion provided to the second shutter member 412 is fitted, instead of the press piece 414B and the press-subjected piece 412B.
When the aperture 408, etc. are closed, the interlocking means is designed so that the projecting portion presses the hole wall of the elongated hole while the difference in rotational locus between the first shutter member 410 and the second shutter member 412 is absorbed by the movement of the projecting portion in the longitudinal direction of the elongated hole, whereby the second shutter member 412 is allowed to be driven by the first shutter member 410 even when the aperture 408, etc. are closed, so that the torsion spring described above is unnecessary.
However, the disc cartridge 400 as described above has the following problems.
First, in the disc cartridge 400, the shutter guide portion 416 and the operating member 418 are fixed to each other as described above, so that there occurs such a case that the rotational direction (the direction of the arrow Q) of the shutter guide portion 416 of the first shutter member 410 and the operating direction (the direction of the arrow P) of the operating member 418 are displaced from each other in the up-and-down direction due to errors in working (in case of being formed integrally) and errors in installation (in case of being fixed separately). That is, there occurs such a case that the longitudinal direction of the shutter guide portion 416 and the longitudinal direction of the operating member 418 are displaced from each other in the intersecting direction (the state that the center line of the operating member 418 is inclined in the height direction with respect to the center line of the shutter guide portion 416).
The displacement in the longitudinal direction between the shutter guide portion 416 and the operating member 418 makes a part of the operating force acting on the operating portion 418A (operating member 418) act as component force in a direction different from that of the rotational force of the shutter guide portion 416, so that not only the operating force required to open/close the aperture 408, etc. is magnified, but also the first shutter member 410 is inclined, thereby disturbing the smooth operation of the first shutter member 410. When the displacement is large, it is difficult to suitably dispose the operating portion 418A fixed to the tip of the operating member 418 in the guide groove 424.
Secondly, in the disc cartridge 400, the first shutter member 410 presses the second shutter member 412 to open the aperture 408, etc., so that large force (operating force) is required to slide the shutter guide portion 416 of the first shutter member 410 along the cylindrical wall 404A. Particularly when the sliding motion is not smooth, the first shutter member 410 may wear the outer peripheral surface of the cylindrical wall 404A to cause occurrence of powder dust (wear powder).
Likewise, particularly when the sliding motion between the upper end face of the shutter guide portion 416 of the first shutter member 410 and the inner surface of the upper shell 402 and the sliding motion between the lower surface of the first shutter member 410 (the shutter main body 414 and the shutter guide portion 416) and the inner surface of the cover member 420 are not smooth, the upper end face and lower end face of the first shutter member 410 wear the inner surface of the upper shell 402 and the inner surface of the cover member 420, so that powder dust, etc. may occur.
Such powder dust, etc. adhere to the recording face of the disc medium 406 to cause occurrence of errors (loss of recording/reproducing signals, so-called drop-out) in the recording/reproducing operation.
Thirdly, in the disc cartridge 400, a corner portion 414D is formed in the shutter main body 414 of the first shutter member 410 so as to be sandwiched between the abutting end face 414A and the end face 414C which abuts against the end portion of the aperture 408, etc. under the state that the aperture 408, etc. is closed, and when the aperture 408, etc. are closed, the corner portion 414D passes the aperture 408, etc. and is accommodated in a reception portion between the lower shell 404 (case) and the cover member 420. Therefore, if the shutter main body 414 constituting the first shutter member 410 is warped, the corner portion 414D may interfere in the reception port of the reception portion (the edge portion of the aperture 408 or the aperture 422).
The interference between the first shutter member 410 (corner portion 414D) and the edge portion of the aperture 408 or aperture 422 not only disturbs the smooth motion of the first shutter member 410, but also makes it impossible to close the aperture 408, etc. That is, the dust-proof performance for the disc medium 406 is lowered, and in accordance with the construction of the drive device, it maybe impossible to unload the disc cartridge 400 from the drive device.
Fourthly, in the conventional cartridge 400 having joint means according to the modification, the elongated hole of the interlocking means is designed to be linear. Therefore, the gap between the elongated hole and the projecting portion is required to be minimized in order to close the aperture 408, etc. with no gap by the abutting of the end faces 414A, 412A of the first and second shutter members 410 and 412 against each other when the opened aperture 408, etc. are closed again.
Therefore, there is a case that the operating force (driving force) to make the first and second shutter members 410, 412 operate interlockingly with each other is magnified, and also the first shutter member 410 and the second shutter member 412 do not operate (interlock with each other) smoothly. Further, in order to make the first and second shutter members 410, 412 interlock with each other properly, excessive dimensional precision and installation precision are required to the interlocking means, resulting in increase of the cost.